1. Field of the Invention
The present invention relates to inflatable protective cushions, and provides an apparatus particularly useful in an airbag for protecting passengers in automotive vehicles. The present invention would also be useful for many types of transportation vehicles, as well as machinery, as a protective device that can be stored compactly.
Inflatable protective cushions used in passenger vehicles are a component of relatively complex systems. The main elements of these systems are: an impact sensing system, an ignition system, a solid propellant material, an attachment device, a system enclosure, and an inflatable protective cushion. Upon sensing an impact, the propellant is ignited causing an explosive release of gases filling the cushion to a deployed state which can absorb the impact of the forward movement of a body and dissipate its energy by means of rapid venting of the gas. The entire sequence of events occurs within about 30 milliseconds. The maximum pressure occurring in the cushion in the inflation event is about 4 psi and increases to about 7-8 psi when impacted by a person. In the un-deployed state, the cushion is stored in or near the steering column, the dashboard, in a door, or in the back of a front seat placing the cushion in close proximity to the person it is to protect.
To provide efficient storage and adequate protection, it is advantageous to have an inflatable protective cushion that has a small volume when not deployed permitting compact storage, low permeability permitting fast inflation, and strength for withstanding inflation pressure and absorbing the impact of a person or an object.
2. Description of Related Art
Many of the traditional driver's side inflatable cushions are of a circular shape constructed with two circular pieces made from a coated fabric made with 420-840 denier nylon yarn as shown in FIG. 1. This product has several deficiencies. First, the design shape may result in a circumferential seam creating preferential locations for failure where the seam is perpendicular to the bias directions of the yarn. Second, that cushion inherently has wrinkles that result in high and low stress areas enhancing the probability of the cushion failing to withstand inflation pressure and impact when deployed. Third, the 420-840 denier fabric and coating on the fabric results in a heavier and bulkier cushion that is not compact when stored. Fourth, the rough surface of the fabric tends to be abrasive leading to facial cuts and abrasions in deployment because of use of the larger denier yarns. Fifth, the coatings that may be on the fabric add significantly to the manufacturing costs. Sixth, the circular shape results in material waste during manufacturing. Finally, the traditional cushions may have discrete vent ports to provide rapid deflation that can cause injury when the hot gases exit the cushion vent ports in a concentrated manner.